This invention relates generally to wind-driven electric power generators, and particularly to a wind turbine having a stationary center vertical support. The invention may also include a shell around which the turbine blades rotate for increasing the wind velocity and air density on the turbine blades, thereby improving overall performance.
Using the energy of the wind for various purposes such as grinding grain and pumping water is a very old idea. More recently, the wind has been harnessed by wind turbines to drive electric generators. The advantages of wind turbines for generating electricity include the fact that the wind itself is cost-free and that the generation process results in no undesirable pollutants such as smoke, radioactivity, chemical waste, or heat.
It is generally recognized that one of the most effective wind turbines for generating electricity are of the Darrieus type in which the turbine blades describe a circular oval shape. The turbine blades are supported by a center vertical post that extends from the base to the top of the apparatus. The turbine blades are arced so that the bottom is attached to the bottom of the center post and the top is attached to the top of the center post and the portion between the top and bottom arcs away from the tower to intercept the wind. The attachments between the tower and the blades are rigid, so that the entire apparatus of center tower and several turbine blades rotates in unison about a vertical axis corresponding to the center tower longitudinal axis. The Darrieus-type design is described further in U.S. Pat. No. 1,835,018 by Darrieus, the contents of which are hereby incorporated by reference.
The ordinary Darrieus design has several problems related to the rotating center tower. One is the cost of the center tower itself. A cost effective Darrieus type turbine is huge--one to two hundred feet tall or more. Further, the turbine blades move quite fast--200 miles per hour or more at the points farthest from the center axis. For the center tower to have the structural ability to rotate, it must be massive. This massiveness results in a very expensive center tower. It also requires a high strength specialized bearing surface at the base to rotatably support the enormous load of the tower and blades. Finally, it adds much to the angular momentum of the entire apparatus and may make it more difficult to control and construct.